Study Of Plate Thickness Measurement System With Laser Illumination

Thickness is an important item index of steel rolling tests, which directly determines the setting of roller gap value. Therefore real-time and online thickness detection is necessary to protect mill and ensure production safety. In this thesis, plate thickness detection methods of non-contact online in metallurgical industry have been compared and analyzed. According to environment of hot-rolled steel plant, a hot-rolled steel plate thickness measuring system with laser illumination and optical imaging is designed.In this system, laser beam obliquely incidence to the test side of steel plate, and the laser band is imaged on CCD target surface by industrial video camera. The thickness of steel plate can be calculated based on the object-image relation with the band's height. For imaging system is titled, test plate's surface is not perpendicular to the optical axis, the relationship between the matter and the image no longer satisfies the linear relationship. Secondly, the steel plate's movement along its width direction brings out-of-focus imaging in different degrees. Therefore, the key point of this thesis is to design and analyze the system optic imaging and obtain the function relation between object and image. Laser triangulation is used to measure the amount of the steel plate's movement along its width direction. The influence of non-vertical to the optical axis and out-of-focus imaging has been analyzed and corrected.The field results show that in the range of 8～120mm thick steel plate, measured deviations are within the scope of±0.5mm,which meet the measuring indicators and requirements of the system. Compared with other current online non-contact thickness measurement methods which are used for hot rolling production line, this method not only greatly reduces influence of the heat radiation but also has the features of reliably function and easy in installing. It has a certain practicality in the industrial field.